Abstract:The phase circulation problem of low-voltage microgrid parallel inverter system seriously affects the power quality and conversion efficiency of the output side of micro-grid. Therefore, sliding mode control (SMC) was introduced to design a compound suppression strategy of phase circulation (CSSPC). Firstly, according to the generation mechanism of phase circulation in parallel system, the inter-phase circulation and intra-phase circulation are modeled, and the inhibition mechanism of different phase circulation is analyzed and given. Then, for the inter-phase circulation of the parallel system, combined with the traditional virtual impedance droop control (VIDC), the robust droop SMC controller was obtained by improving the design: bus voltage response, droop loop output accuracy and virtual induced reactance regulation, in order to improve the power distribution accuracy of the parallel system and restrain the inter-phase circulation; The parametric stability of the robust droop SMC controller is analyzed based on the theory of small signal perturbation. For the intra-phase circulation of parallel system, a zero-sequence voltage SMC suppressor is designed to dynamically adjust the action time of zero vector in space vector pulse width modulation (SVPWM) and to indirectly suppress the intra-phase circulation of parallel system by eliminating zero sequence voltage. Finally, simulations are designed, and the results to show that the CSSPC strategy can control the system inter-phase and intra-phase circulation coefficients within 1.49% and 0.72% respectively, which proves the effectiveness of the proposed strategy.